The disclosure of Japanese Patent Application No. 2001-215662 filed on Jul. 16, 2001 and No. 2001-320692 filed on Oct. 18, 2001, each including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates generally to fluid-filled vibration-damping devices exhibiting vibration-damping effect on the basis of flows of non-compressible fluid filled therein, and a method of controlling these devices. More particularly, the present invention is concerned with such a fluid-filled vibration-damping device that is suitably applicable to an engine mount, a body mount or the like for use in an automotive vehicle, and a method of controlling the same.
2. Description of the Related Art
A fluid-filled vibration-damping device is known as one type of a vibration-damping device interposed between two members of a vibration system for elastically connecting the two members, or for mounting one of the two members of the vibration system on the other member in a vibration-damping fashion. The known fluid-filled vibration-damping device includes: a first mounting member adapted to be attached to one of the two members of the vibration system; a second mounting member adapted to be attached to the other member of the vibration system; a rubber elastic body elastically connecting the first and second mounting members; a pressure-receiving chamber partially defined by the rubber elastic body and filled with a non-compressible fluid; an equilibrium chamber partially defined by a flexible layer and filled with the non-compressible fluid; and an orifice passage permitting a fluid communication between the pressure-receiving chamber and the equilibrium chamber. The known fluid-filled vibration-damping device is capable of exhibiting a desired vibration-damping effect on the basis of flows of the fluid through the orifice passage, and is favorably used as an engine mount or other damping members for use in an automotive vehicle.
Generally, a fluid-filled vibration-damping device when used as a vehicle engine mount is required to exhibit different damping characteristics depending on the type of the input vibrations having different frequencies and amplitudes. However, the range of frequency of the input vibrations that can be effectively damped by fluid flows through an orifice passage is relatively narrow. Therefore, a fluid-filled vibration-damping device using a single orifice passage is generally incapable of exhibiting desired damping characteristics to a satisfactory extent.
In view of the above problem, there has been proposed a mount structure comprising a plurality of orifice passages each permitting a fluid communication between the pressure-receiving chamber and the equilibrium chamber, and being tuned to a plurality of frequency ranges to be damped or isolated, respectively. Based on the resonance of the fluid flowing through the plurality of orifice passages, this mount structure can exhibit a vibration-damping effect with respect to the input vibrations over a wide or a plurality of different frequency bands to which the plurality of orifice passages are respectively tuned.
However, in the mount structure constructed as described above, a resistance to flow of the fluid through the orifice passage tuned to a low frequency range is made higher than that of the orifice passage tuned to a high frequency range. Accordingly, the fluid is prone to flow through the orifice passage tuned to the high frequency range, rather than the orifice passage tuned to the low frequency range, resulting in insufficient damping effect based on the flows of the fluid through the orifice passage tuned to the low frequency range.
JP-A-8-270718 discloses an example of another type of the fluid-filled vibration-damping device, which has been proposed to cope with the above-described problem. The disclosed damping device includes an orifice closing member adapted to bring the orifice passage tuned to the high frequency range into an operable state or an inoperable state, thus being capable of selectively effecting the orifice passage tuned to the low frequency range and the orifice passage tuned to the high frequency range.
In the case where the fluid-filled vibration-damping device uses three or more orifice passage, two or more orifice closing members need to be disposed within the device, leading to a complicated structure and a sophisticated manner of control of the operation of the device. Thus, the conventional fluid-filled vibration-damping device suffers from difficulty in exhibiting excellent damping effect with respect to input vibrations over three or more different frequencies.
If all of the plurality of orifice passages tuned to different frequency ranges are held in their operable states simultaneously, then the orifice passage, which is tuned to the lowermost frequency range, and accordingly has a high resistance to flow of the fluid therethrough, inevitably suffers from lack of an amount of flow of the fluid therethrough. For the above reasons, it is significantly difficult to achieve different damping effect with respect to input vibrations having different frequencies, simultaneously, even in the fluid-filled vibration-damping device equipped with the plurality of orifice passages and the orifice closing members.
It is therefore one object of this invention to provide a fluid-filled vibration-damping device that is novel and simple in construction and that is capable of exhibiting an excellent vibration-damping effect input vibrations over a plurality of frequencies or a wide range of frequency of the input vibrations.
It is another object of the invention to provide a method of controlling operation of the fluid-filled vibration-damping device of the invention.
The above and/or optional objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A fluid-filled vibration-damping device for connecting two members in a vibration-damping fashion, that includes: (a) a first mounting member and a second mounting member disposed in a mutually spaced-apart relationship with each other and adapted to be attached to the two members, respectively; (b) an elastic body elastically connecting the first and second mounting members, and partially defining (c) a pressure-receiving chamber filled with a non-compressible fluid whose pressure varies upon application of a vibrational load to the pressure-receiving chamber; (d) a flexible diaphragm partially defining an equilibrium chamber filled with the non-compressible fluid and whose volume is variable; (e) a first orifice passage for fluid communication between the pressure-receiving chamber and the equilibrium chamber; (f) a second orifice passage for fluid communication between the pressure-receiving chamber and the equilibrium chamber, the second orifice passage being tuned to a frequency range that is higher than a frequency range to which the first orifice passage is tuned; (g) a shut-off valve mechanism operable to selectively bring the second orifice passage to an operable state and an inoperable state, while permitting a fluid communication through the first orifice passage; (h) an elastic oscillation plate partially defining the pressure-receiving chamber so that a fluid pressure in the pressure-receiving chamber acts on one of opposite surfaces of the elastic oscillation plate; and (i) a working air chamber partially defined by an other one of opposite surfaces of the elastic oscillation plate, which is remote from the pressure-receiving chamber, the elastic oscillation plate being oscillated by a periodic change of an air pressure in the working air chamber.
The fluid-filled vibration-damping device according to this mode of the invention can exhibit an intended vibration-damping effect with respect to low frequency vibrations on the basis of flows of the fluid through the first orifice passage with the second orifice passage being inoperative by means of the shut-off valve mechanism, and can exhibit an intended desired vibration isolation effect with respect to higher frequency vibrations on the basis of flows of the fluid through the second orifice passage with the second orifice passage being operative by means of the shut-off valve mechanism. In addition, the fluid-filled vibration-damping device of this mode is capable of exhibiting active damping effect by oscillating the elastic oscillating plate with the help of periodic air pressure change induced in the working air chamber, also, making it possible to improve vibration-damping or isolating effect on the basis of the fluid flowing through the first or second orifice passage at the frequency to which the first or second orifice passage is tuned, or alternatively to exhibit a vibration-damping or isolating effect at a frequency that is different from the frequency ranges to which the first and second orifice passages are tuned.
In the fluid-filled vibration-damping device of this mode of the invention, the second orifice passage is selectively controlled to be operative or inoperative for permitting or inhibiting the fluid communication therethrough, allowing the vibration-damping device to selectively exhibit passive damping effect with the help of fluid flows through the first and second orifice passages. In addition, the fluid-filled vibration-damping device of this mode of the invention is capable of exhibiting the active damping effect at a suitable opportunity by oscillating the elastic oscillation plate. That is, the present vibration-damping device can utilize both of passive and active damping effect, making it possible to selectively exhibit appropriate damping effect at three or more different frequency ranges of vibrations to be damped, or alternatively to simultaneously exhibit excellent vibration-damping effect with respect to vibrations having different frequencies.
(2) A fluid-filled vibration-damping device according to the above-indicated mode (1), wherein one of opposite openings of the second orifice passage for fluid communication with the equilibrium chamber is located in a position that is different from a position where one of opposite openings of the first orifice passage for fluid communication with the equilibrium chamber is located, the vibration-damping device further comprising a pneumatically operated actuator disposed to be opposed to the one of opposite openings of the second orifice passage with the flexible diaphragm interposed therebetween, the pneumatically operated actuator being operable to displace the flexible diaphragm to selectively be pressed onto and retracted from the one of opposite openings of the second orifice passage, in order to selectively bring the second orifice passage to the operable state and the inoperable state. According to this mode of the invention the shut-off valve mechanism can be embodied by utilizing the pneumatically operated actuator that is simple in construction and light in weight. In this respect, air pressure to be applied to the working air chamber can also be utilized to operate the pneumatically operated actuator, making it possible to further simplify the structure of the fluid-filled vibration-damping device of this mode of the invention.
(3) A fluid-filled vibration-damping device according the above-indicated modes (1) or (2), wherein the pressure-receiving chamber is divided into a primary fluid chamber partially defined by the elastic body and an auxiliary fluid chamber partially defined by the elastic oscillation plate, the vibration-damping device further comprising a third orifice passage for fluid communication between the primary fluid chamber and the auxiliary fluid chamber, which is tuned to a frequency range higher than the frequency range to which the second orifice passage is tuned. In the fluid-filled vibration-damping device constructed according to this mode of the invention, a fluid pressure variation induced in the auxiliary fluid chamber by the oscillation of the elastic oscillation member can be effectively transmitted to the primary fluid chamber through the third orifice passage, by suitably tuning the third orifice passage, thus improving pressure transmitting efficiency. Alternatively, the third orifice passage is capable of restricting or preventing that higher frequency components contained in the fluid pressure variation are undesirably transmitted from the auxiliary fluid chamber to the primary fluid chamber.
In order to restrict or prevent undesirable transmission of the higher frequency components contained in the fluid pressure variation caused in the auxiliary fluid chamber by the oscillation of the elastic oscillation member to the primary fluid chamber, the third orifice passage is desirably tuned to a frequency range that is generally equal to or slightly higher than a highest value of a frequency range of the active damping effect as a result of oscillation of the elastic oscillation plate. Further, at around tuning frequency of the third orifice passage, the fluid pressure variation induced in the auxiliary fluid chamber can be transmitted to the primary fluid chamber with an improved efficiency with the help of resonance or flows of the fluid through the third orifice passage.
(4) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(3), wherein the vibration-damping device is applied to an engine mount for use in an automotive vehicle, and the first, second and third orifice passages are respectively tuned to a low frequency range corresponding to engine shakes, an intermediate frequency range corresponding to engine idling vibrations, and a high frequency vibrations corresponding to booming noises that are produced during running of the vehicle. This arrangement allows the fluid-filled vibration-damping device to be provided as an engine mount that exhibits excellent damping effect with respect to vibrations to be damped in the automotive vehicle.
(5) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(4), wherein the second mounting member includes a cylindrical portion and one of axially opposite opening of the cylindrical portion is opposed to the first mounting member with a spacing therebetween, and the elastic body elastically connecting the first and second mounting members fluid-tightly closes the one of axially opposite opening of the cylindrical portion of the second mounting member, while the flexible diaphragm fluid-tightly closes an other one of axially opposite opening of the cylindrical portion of the second mounting member, wherein the vibration-damping device further comprises a partition member supported by the cylindrical portion of the second mounting member and being disposed between the elastic body and the flexible diaphragm so that the pressure-receiving chamber and the equilibrium chamber is disposed on the opposite sides of the partition member, and wherein the first orifice passage is formed in an outer circumferential portion of the partition member so as to extend circumferentially, and the second orifice passage is formed in a central portion of the partition member, while the elastic oscillation plate is disposed in and supported by a portion of the partition member where the first and second orifice passages are not disposed, such that the portion of the partition member cooperates with the other one of opposite surfaces of the elastic oscillation plate to form the working air chamber. In this arrangement, the partition member, which separates the pressure-receiving chamber and the equilibrium chamber from each other, is efficiently utilized to form the first and second orifice passages, the working air chambers and the like within the cylindrical portion of the second mounting member with effective space utilization, permitting the vibration-damping device to be compact in its entire size.
(6) A fluid-filled vibration-damping device according to any one of the above-indicated modes (1)-(5), wherein the shut-off valve mechanism comprises a pneumatically operated shut-off valve that is operable to bring the second orifice passage to the inoperable state by an atmospheric pressure applied thereto and to the operable state by a negative pressure applied thereto, the vibration-damping device further comprising: a first pressure control valve having an active-side port for communication with the working air chamber, an atmosphere-side port for communication with the atmosphere and a vacuum-side port for communication with a vacuum source, and being operable to alternately connect the active-side port to the atmosphere-side port and the vacuum-side port for alternately applying an atmospheric pressure and a negative pressure to the working air chamber, in order to control oscillation of the elastic oscillation plate based on a periodic air pressure change induced in the working air chamber; and a second pressure control valve having an active-side port for communication with the pneumatically operated shut-off valve, an atmosphere-side port for communication with the atmosphere and a vacuum-side port for communication with a vacuum source, and being operable to alternately connect the active-side port to the atmosphere-side port and the vacuum-side port for alternately applying the atmospheric pressure and the negative pressure to the pneumatically operated shut-off valve, in order to selectively bring the second orifice passage to the operable state and the inoperable state, wherein the atmosphere-side port of the first pressure control valve is connected to the active-side port of the second pressure control valve so that the atmospheric pressure is applied to the atmosphere-side port of the first pressure control valve through the second pressure control valve. In a state where the second pressure control valve is held in a position for permitting a connection between the active-side port and the vacuum-side port, while the first pressure control valve is held in a position for permitting a connection between the active-side port and the atmosphere-side port, for example, the second orifice passage is held in its operable state for permitting fluid flows therethrough, while the elastic oscillation plate is held in a state of vacuum suction due to the negative pressure applied to the working air chamber, thus allowing the elastic oscillation plate to acquire stiffer spring characteristics.
That is, the fluid-filled vibration-damping device constructed according to the mode (6) of the invention is capable of restricting or prohibiting the elastic deformation or displacement of the elastic oscillation plate that functions to absorb the pressure variation induced in the pressure-receiving chamber. This arrangement is effective to obtain a sufficient amount of fluid flows through the second orifice passage, assuring an improved passive damping effect on the basis of fluid flows through the second orifice passage.
(7) A method of controlling a fluid-filled vibration-damping device as defined in the above-indicated mode (4) or (6), comprising the steps of: when the vehicle is idling, bringing the second orifice passage to the operable state; when the vehicle is running, bringing the second orifice passage to the inoperable state by means of the shut-off valve mechanism; and at least when the vehicle is running, applying to the working air chamber a periodic air pressure change at a frequency corresponding to that of vibrations to be damped in order to oscillate the elastic oscillation plate. According to the control method of this mode, the fluid-filled vibration-damping device as defined in the above indicated mode (4) or (6) can exhibit excellent damping effect with respect to low frequency vibrations such as engine shakes excited in the running condition of the vehicle, and intermediate frequency vibrations such as engine idling vibrations excited in the idling condition of the vehicle, by selectively utilizing the fluid flows through the first orifice passage and the fluid flows through the second orifice passage depending upon driving conditions of the vehicle. In the running condition of the vehicle, moreover, the fluid-filled vibration-damping device can exhibit active damping effect on the basis of the oscillation of the elastic oscillation plate with respect to intermediate or high frequency vibrations, as well as the passive damping effect with respect to low frequency vibrations on the basis of fluid flows through the first orifice passage. Therefore, the fluid-filled vibration-damping device as defined in the mode (4) or (6), which is operated according to the control method of the mode (7), is able to exhibit excellent damping effect over a wide range of frequency or a plurality of frequencies of the input vibrations. It is noted that the term xe2x80x9cthe vehicle is idlingxe2x80x9d should be interpreted to mean the driving state of the vehicle where the engine is idling with the vehicle stopped.
(8) A method of controlling a fluid-filled vibration-damping device according to the above-indicated mode (7), further comprising the steps of: when the vehicle is idling, bringing the second orifice passage to the operable state while applying to the working air chamber a periodic air pressure change at a frequency corresponding to that of the engine idling vibrations in order to oscillate the elastic oscillation plate; and when the vehicle is running, bringing the second orifice passage to the inoperable state by means of the shut-off valve mechanism, while applying to the working air chamber a periodic air pressure change at a frequency corresponding to that of the booming noises in order to oscillate the elastic oscillation plate. According to the control method of this mode, the fluid-filled vibration-damping device can exhibit excellent damping effect with respect to idling vibrations by utilizing a passive damping effect on the basis of fluid flows through the second orifice passage as well as an active damping effect on the basis of the oscillation of the elastic oscillation plate, when the vehicle is idling. When the vehicle is running, on the other hand, the fluid-filled vibration-damping device can exhibit excellent damping effect with respect to low frequency vibrations such as engine shakes and intermediate and high frequency vibrations such as booming noises, by utilizing a passive damping effect on the basis of the fluid flows through the first orifice passage and the active damping effect on the basis of oscillation of the elastic oscillation plate. Thus, the present control method allows the fluid-filled vibration-damping device to exhibit desired vibration-damping effect over a wide range of frequency or a plurality of frequencies of the input vibrations desired to be damped in the vehicle.
(9) A method of controlling a fluid-filled vibration-damping device according to the above-indicated mode (7), further comprising the steps of: when the vehicle is idling, bringing the second orifice passage to the operable state and applying a negative pressure to the working air chamber; and when the vehicle is running, bringing the second orifice passage to the inoperable state by means of the shut-off valve mechanism, while applying to the working air chamber a periodic air pressure change at a frequency corresponding to that of vibrations to be damped in order to oscillate the elastic oscillation plate. According to the control method of this mode, when the vehicle is idling, the negative pressure is applied to the working air chamber to hold the elastic oscillating plate in a state of vacuum suction, thereby providing stiffer spring characteristics of the elastic oscillating plate. This arrangement makes it possible to restrict or prevent absorption of the internal pressure changes in the pressure-receiving chamber based on the elastic deformation or elastic displacement of the oscillation rubber plate, thus assuring a sufficient amount of flows of the fluid through the second orifice passage, resulting in an intended passive vibration damping effect with respect to the engine idling vibrations. When the vehicle is running on the other hand, the fluid-filled vibration-damping device can exhibit excellent damping effect with respect to low frequency vibrations such as engine shakes and intermediate and high frequency vibrations such as booming noises, by utilizing a passive damping effect on the basis of the fluid flows through the first orifice passage and the active damping effect on the basis of oscillation of the elastic oscillation plate. Thus, the present control method allows the fluid-filled vibration-damping device to exhibit desired vibration-damping effect over a wide range of frequency or a plurality of frequencies of the input vibrations desired to be damped in the vehicle.
Preferably, the control method according to this mode (9) of the invention is desirably applied to control the fluid-filled vibration-damping device constructed according to the above-described mode (6). This makes it easy to control the second orifice passage to selectively be operative and inoperative, and to control air pressure in the working air chamber.